str(binVer)
'data.frame':   6976 obs. of  39 variables:
 $ mutdat       : Date, format: "2017-01-10" "2017-01-10" ...
 $ muttijd      : chr  "11505800" "14050100" "15081000" "14242900" ...
 $ mutsrt       : num  2 2 2 2 2 2 2 2 2 2 ...
 $ gebdat       : Date, format: "1998-09-16" "1993-03-21" ...


binVer$mutdat
 NULL

binVer[1]
         mutdat
1    2017-01-10
2    2017-01-10
3    2017-01-06
4    2017-01-06

binVer$Age<- age(binVer$gebdat, binVer$mutdat)
Error in as.POSIXlt.default(to) :
  do not know how to convert 'to' to class “POSIXlt”